In known arrangements of this type, the index is generally formed by a hand which is borne by a cannon wheel arranged on the hour wheel pipe and which may be displaced by turning a knob.
Among these arrangements, there are certain where the two contact points are situated on the facing surfaces of the hour wheel and the wheel which bears the alarm hand, otherwise known as the alarm wheel and where this latter meshes directly with a pinion mounted on the same rotatable stem as the setting knob.
These arrangements are thus very simple and very economical.
The purpose of the invention is to provide an alarm arrangement which may be still more simple.